Multi-subscriber identity module (SIM) wireless communication devices have become increasing popular because of their flexibility in service options and other features. One type of multi-SIM wireless communication device, a multi-SIM multi-standby (MSMS) wireless communication device (e.g., a dual-SIM dual-standby (DSDS) device), enables two SIMs to be in idle mode waiting to begin communications, but only allows one SIM at a time to participate in an active communication due to sharing of a single radio frequency (RF) resource (e.g., a transceiver). Other multi-SIM devices may extend this capability to more than two SIMs and may be configured with any number of SIMs greater than two (i.e., multi-SIM multi-standby wireless communication devices).
Wireless communication networks (referred to simply as “wireless networks” herein) are widely deployed to provide various communication services such as voice, packet data, broadcast, messaging, and so on. Wireless networks may be capable of supporting communication for multiple users by sharing the available network resources. Such sharing of available network resources may be implemented by networks using one or more multiple-access wireless communications protocols, such as Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Frequency Division Multiple Access (FDMA). These wireless networks may also utilize various radio technologies, including but not limited to Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), CDMA2000, Advanced Mobile Phone Service (AMPS), General Packet Radio Services (GPRS), Long Term Evolution (LTE), High Data Rate (HDR) technology (e.g., 1×EV technology), etc.
Since an MSMS wireless communication device typically uses a single RF resource to communicate over the multiple SIMs and/or networks, the device actively communicates using a single SIM and/or network at a given time. For example, while one SIM is participating in active communication on a particular network, the second SIM may be in idle mode camped on a serving cell of the same or different network. As such, with an active data communication on one SIM (e.g., the first SIM), the wireless communication device may periodically tune away to a network associated with another SIM (e.g., the second SIM) to monitor signals or acquire a connection. During idle mode on a SIM, the MSMS wireless communication device will periodically determine whether there is a better cell on which to camp and receive service. Reselection to a new cell may be triggered if the received signal level for any neighbor is better than that of the current serving cell for a period of time (e.g., at least five seconds in a GSM system).
In order to minimize delay in service that can occur in initial cell selection or reselection, the MSMS wireless communication device can implement early camping for a SIM by initially receiving sufficient system information to process a paging channel for the target cell, and if a paging message is received, save the page message for processing after completion of the cell selection/reselection. This early camping procedure may reduce the chance of missing a paging message to the second SIM during initial cell selection or cell reselection. However, some of the remaining system information for the second SIM may not be received due to conflicts in timing between the broadcast of the system information and the active communication on the first SIM. As a result, the wireless communication device may be unable to process the paging message for the second SIM, in which case the paging message will be discarded, thereby degrading performance for receiving mobile terminating calls on the device.